1. Field of the Invention
The invention relates to a bioreactor and in particular to a bioreacter containing a means for the vapor sterilization of the inner space of the reactor vessel and of the tubes extending beneath the fluid level of said vessel.
2. Description of Related Art
Bioreactors are used for the culture and growth of biological substances such as cells and enzymes. Their operation requires absolute freedom from contamination. Bioreactors are made of vapor-sterilizable materials; e.g., special steel. To eliminate undesired germs, sterilization is typically performed by vapor which is either formed at a temperature of about 121.degree. C in the vessel or which is introduced into the vessel under pressure. The function of the vapor is to sterilize not only the inner space of the vessel, but also the interior of the tubing inside the vessel and, in particular, the immersion tubes. It is relatively simple to sterilize an empty bioreactor, while difficulties arise if a fluid; e.g., a nutrient broth, is contained in the bioreacter because, due to vapor pressure, fluid is driven out through the tubes to be sterilized, or, if the tubes are closed, the air space within them is not sterilized by the vapor.
It has been known to provide a separate vapor connection at the vessel for the vapor sterilization of a bioreactor. However, in such a case, a higher expenditure is involved with the vessel and the vapor is introduced into the fluid present in the vessel. Very often, the introduction of vapor into the fluid is undesired.
It has been further known to provide, in the wall of the head space of the vessel, a diaphragm which is pierced by a hollow needle to introduce vapor (it being necessary to previously sterilize the needle by a flame). However, contamination due to the introduction of the needle into the interior of the vessel cannot be entirely excluded. The tubes, filters and other means to be connected must be previously sterilized separately.
According to DE-OS 35 39 798, there has been known a valve for sterilizing a bioreactor which includes in its cover the valve chamber. A part of the valve chamber which projects into the head space of the reactor is provided with openings. A slide is displaceable in a bore of the valve chamber. The external end of the slide may be joined to a vapor line. The inner end of the slide is provided with two axially spaced seals. In the operating position of the valve, when the slide is lowered, the channel of the slide is connected to a tube extending as far as to the bottom of the vessel. In the sterilizing position, when the slide is lifted, vapor fed through the channel of the slide flows through the free opening of the valve chamber into the head space of the vessel. It is a disadvantage of said valve that, in the sterilizing position, the slide section between the two seals is not contacted by vapor and, accordingly, remains unsterilized. In the operating position, said section communicates through the openings with the sterilized region of the vessel, and a contamination of the vessel content may occur.
It is an object of the present invention to provide a bioreacter in which, during sterilization, all of the areas which communicate with the vessel region in the operating phase are sterilized, thus safely inhibiting any contamination.